1. Field of the Invention
The invention relates to compressors of gas turbine engines, and is particularly concerned with the mounting of a stage of variably settable stator blades in the compressor.
2. Discussion of the Prior Art
Adjustment of the orientation of the stator blades of various compressors stages is particularly desirable when, for example, at a given rating, the greatest possible pressure is sought for the various stages while retaining an adequate margin for surging.
Variable settable stator blades are generally rotated by links external of the stator casing and connected together by a control ring. In order for each blade to be rotatable, it is generally provided with journals at its head and root which are rotatably mounted in bushes or journal boxes.
French Patent No. 2 524 934 describes a blade having a root journal box with a bore in which the blade root journal rotates, the journal box having, if desired, a diamond-shaped face of which the parallel edges perform the function of limiting the maximum possible angular movement of the blade so that, should the control lever of one of the blades break, the blade would not feather or set itself across the flow of air through the stage, which would probably lead to surging of the entire stage.
U.S. Pat. No. 3,029,067 discloses settable blades against which a stop member can act to limit the possible rotation of a blade. However this arrangement is a fairly complex assembly and is limited to a compressor of the centrifugal type.